In a twin roll-type sheet continuous casting apparatus, a pair of cooled casting rolls disposed horizontally and parallel to each other are rotated in opposite directions, respectively, and molten metal is continuously supplied between the pair of rotating casting rolls to continuously cast a sheet, and the cast sheet is extended to a coiler through a group of pinch rollers and transfer rollers, and is continuously taken up by the coiler.
Usually, in the above apparatus, a dummy sheet is used when starting the casting of the sheet. The dummy sheet is beforehand joined to a leading end portion of the cast sheet, and a leading end portion of this dummy sheet is wound around the coiler through the group of pinch rollers and transfer rollers. When the casting of the sheet is started, the dummy sheet is taken up by the coiler to guide the leading end portion of the cast sheet so that it can be taken up by the coiler.
When the cast sheet is ruptured, the operation of the apparatus is stopped, and the dummy sheet is again joined to the leading end portion of the cast sheet as described above. Then, the operation is resumed.
Twin roll-type sheet continuous casting apparatuses which do not need the use of a dummy sheet are proposed in Japanese Patent Unexamined Publication No. 60-177935 and Japanese Utility Model Unexamined Publication No. 59-165754, respectively.
The former apparatus includes a device for supplying two strip-like sheets which device is disposed below a pair of casting rolls. When the casting of a sheet is started, the two strip-like sheets are placed on a group of transfer rolls, and leading end portions thereof are wound around a coiler. A leading end portion of a sheet cast by the casting rolls is sandwiched between the two strip-like sheets, and is taken up, together with the strip-like sheets, by the coiler. After the leading end portion of the cast sheet is taken up by the coiler, the supply of the strip-like sheets is stopped, and only the cast sheet is taken up by the coiler. Namely, in this apparatus, since the leading end portion of the cast sheet is guided to the coiler by the two strip-like sheets, the dummy sheet is not needed. However, when a rupture of the cast sheet occurs, the operation of the apparatus must be stopped in order to set the strip-like sheets.
The latter apparatus includes a water passage in which a fluid flows at a speed higher than the speed of transfer of a cast sheet, this water passage serving as a transfer device for transferring the cast sheet to a coiler. When the casting of the sheet is started, the leading end portion of the cast sheet is transferred to the coiler by the fluid, and is taken up by the coiler. Then, the cast sheet is continuously taken up by the coiler. Since the leading end portion of the cast sheet is guided to the coiler by the fluid, the dummy sheet is not needed. Further, even if a rupture of the cast sheet occurs, the leading end portion of the cast sheet is again transferred to the coiler by the fluid, and therefore the operation of the apparatus does not need to be stopped.
These apparatuses are both suited for the continuous casting of a sheet of a ductile material such as stainless steel, and are not suited for the casting of a sheet of a brittle material such as Fe-Cu alloy. The reason for this is that when the cast sheet is to be wound on the coil, tension is applied to the cast sheet. In the case of the ductile material, the cast sheet is hardly ruptured by this tension. However, in the case of the brittle material, the sheet is ruptured immediately when the tension is applied thereto.
Up to now, any twin roll-type sheet continuous casting apparatus capable of continuously casting a sheet of a brittle material has not been proposed.